--auto-servernum argument is deprecated

[assafna]

According to "xvfb-run": --auto-servernum - try to get a free server number, starting at --server-num (deprecated, use --auto-display instead).

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If your PR modifies code of the plotly package, we have a different checklist
below :-).

Documentation PR

• I've seen the doc/README.md file
• This change runs in the current version of Plotly on PyPI and targets the doc-prod branch OR it targets the master branch
• If this PR modifies the first example in a page or adds a new one, it is a px example if at all possible
• Every new/modified example has a descriptive title and motivating sentence or paragraph
• Every new/modified example is independently runnable
• Every new/modified example is optimized for short line count and focuses on the Plotly/visualization-related aspects of the example rather than the computation required to produce the data being visualized
• Meaningful/relatable datasets are used for all new examples instead of randomly-generated data where possible
• The random seed is set if using randomly-generated data in new/modified examples
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• Imports are plotly.graph_objects as go / plotly.express as px / plotly.io as pio
• Data frames are always called df
• fig = <something> call is high up in each new/modified example (either px.<something> or make_subplots or go.Figure)
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• Hex codes for colors are not used in any new/modified example in favour of these nice ones

Code PR

• I have read through the contributing notes and understand the structure of the package. In particular, if my PR modifies code of plotly.graph_objects, my modifications concern the codegen files and not generated files.
• I have added tests (if submitting a new feature or correcting a bug) or
  modified existing tests.
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  new tutorial notebook (please see the doc checklist as well).
• I have added a CHANGELOG entry if fixing/changing/adding anything substantial.

[assafna]

recheck

[gvwilson]

thanks @assafna for submitting this - we are no longer supporting Orca, so I'm going to close this one as stale. My apologies for taking so long to get to it. Thanks - @gvwilson